I'm trying to implement (or make sure that I'm correctly following) email sending best practices to improve deliverability, but
the role of
the smtp server's host name vs
the domain name of
the From: email address seems to be unclear, even after reading dozens of people's articles/input.
Specifically, I understand that to satisfy
the reverse DNS check, there must be a PTR record for
the IP address of
the sending machine that yields a domain name that matches
the host name of
the sending machine / SMTP server. Some say it needs to match
the one given by
the "hostname" command, most say it's
the one provided with
the HELO / EHLO statement, and this guy even says they MUST be
the same (according to / enforced by what, I don't know; that's only a minor point of confusion, anyhow).
First, what I can't find anywhere is whether or not
the domain name of
the From: email address needs to match
the domain name of
the SMTP server.
So in my case, I have a VPS with linode. It primarily hosts a particular domain of mine, example.com, but I also sometimes do work on other projects:
foo.com and bar.com.
So what I'm wondering is if I can just leave
the default linode PTR record (which resolves to abc.def.linode.com), make sure that abc.def.linode.com is what my mail server (qmail) is configured to say at HELO, and then proceed to use it to send out emails for example.com,
foo.com, et al.
If so, then I am confused by
the advice given here, specifically (in a listing of bad case scenarios):
No SPF record for
the domain being used in
the HELO command
Why would THAT domain need an SPF record? And if it does, which domain should it provide whitelisting for:
the HELO domain, or
the domain of
the From: email address (envelope sender)? Also, which domain would need to accept mail sent to
[email protected]?
If
the domains must be
the same, that would seem rather limiting to me, because then for every domain you wanted to send email from, you'd have to get another IP address for it. It would also compromise or ruin one's ability to do non-email sending things (e.g. wget) relatively anonymously. However,
the upside--if this is
the case--is that it would make for a far less confusing setup.
I'm currently using
the linode.com SMTP+PTR domain and example.com From: address combination without much of any deliverability issue, but my volume is very low and I'd like to know if someone out there has experience with larger volumes and has specifically tested
the difference and/or has inside knowledge and/or has an authoritative answer (and source) for this particular question. I'm happy to clarify anything, let me know. Thanks in advance.
